Effective Bandwidth Path Metric and Path Computation Method for Wireless Mesh Networks with Wired Links

ABSTRACT

Enhanced mesh network performance is provided by computation of a path metric with respect to multi-hop paths between nodes in a mesh network and determination of a path through the mesh network that is optimal according to the path metric. Information is communicated in the mesh network according to the determined path. Nodes in the mesh network are enabled to communicate via one or more wireless links and/or one or more wired links. The path metric optionally includes an effective bandwidth path metric having elements (listed from highest to lowest conceptual priority) including an inverse of a sustainable data rate, a number of wireless links, and a number of wireless and wired links. The sustainable data rate is a measure of communication bandwidth that is deliverable by a path for a period of time. Accounting is made for interference between contiguous wireless links operating on the same channel.

CROSS REFERENCE TO RELATED APPLICATIONS

Priority and Benefit claims for this application are made in theaccompanying Application Data Sheet. To the extent permitted by the typeof the instant application, this application incorporates by referencefor all purposes the following applications, all owned by the owner ofthe instant application:

-   India Application Serial No. 627/DEL/2006 (Docket No.    FT.2006.01-IN), filed Mar. 9, 2006, first named inventor Bhargav    Ramachandra Bellur, and entitled EFFECTIVE BANDWIDTH PATH METRIC AND    PATH COMPUTATION ALGORITHM FOR WIRELESS MESH NETWORKS WITH WIRED    LINKS;-   U.S. application Ser. No. 11/618,073 (Docket No. FT.2006.01-US, now    U.S. Pat. No. 7,768,926), filed Dec. 29, 2006, first named inventor    Bhargav Ramachandra Bellur, and entitled EFFECTIVE BANDWIDTH PATH    METRIC AND PATH COMPUTATION METHOD FOR WIRELESS MESH NETWORKS WITH    WIRED LINKS; and-   U.S. application Ser. No. 12/845,669 (Docket No. FT-06-01-01US, now    U.S. Pat. No. 8,498,211), filed Jul. 28, 2010, first named inventor    Bhargav Ramachandra Bellur, and entitled EFFECTIVE BANDWIDTH PATH    METRIC AND PATH COMPUTATION METHOD FOR WIRELESS MESH NETWORKS WITH    WIRED LINKS.

BACKGROUND

1. Field

Advancements in wireless networks are needed to provide improvements inperformance, efficiency, and utility of use.

2. Related Art

Unless expressly identified as being publicly or well known, mentionherein of techniques and concepts, including for context, definitions,or comparison purposes, should not be construed as an admission thatsuch techniques and concepts are previously publicly known or otherwisepart of the prior art. All references cited herein (if any), includingpatents, patent applications, and publications, are hereby incorporatedby reference in their entireties, whether specifically incorporated ornot, for all purposes. Nothing herein is to be construed as an admissionthat any of the references are pertinent prior art, nor does itconstitute any admission as to the contents or date of actualpublication of these documents.

SYNOPSIS

The invention may be implemented in numerous ways, including as aprocess, an article of manufacture, an apparatus, a system, acomposition of matter, and a computer readable medium such as a computerreadable storage medium or a computer network wherein programinstructions are sent over optical or electronic communication links. Inthis specification, these implementations, or any other form that theinvention may take, may be referred to as techniques. In general, theorder of the steps of disclosed processes may be altered within thescope of the invention. The Detailed Description provides an expositionof one or more embodiments of the invention that enable improvements inperformance, efficiency, and utility of use in the field identifiedabove. The Detailed Description includes an Introduction to facilitatethe more rapid understanding of the remainder of the DetailedDescription. The Introduction includes Example Embodiments of systems,methods, and computer readable media in accordance with the conceptstaught herein. As is discussed in more detail in the Conclusions, theinvention encompasses all possible modifications and variations withinthe scope of the issued claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an embodiment of a mixed wireless and wired meshnetwork.

FIG. 2 illustrates portions of the mesh network of FIG. 1 for an examplecalculation of an effective bandwidth metric.

FIG. 3 illustrates portions of the mesh network of FIG. 1 for an examplecalculation of optimal paths.

FIGS. 4A-D illustrate various aspects of an embodiment of a pathcomputation technique.

FIG. 5 illustrates selected details of hardware aspects of an embodimentof a node.

FIG. 6 illustrates selected details of software aspects of an embodimentof a node.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the invention isprovided below along with accompanying figures that illustrate theprinciples of the invention. The invention is described in connectionwith the embodiments. It is well established that it is neithernecessary, practical, or possible to exhaustively describe everyembodiment of the invention. Thus the embodiments herein are understoodto be merely illustrative, the invention is expressly not limited to orby any or all of the embodiments herein, and the invention encompassesnumerous alternatives, modifications and equivalents. To avoid monotonyin the exposition, a variety of word labels (including but not limitedto: first, last, certain, particular, select, and notable) may beapplied to separate sets of embodiments; as used herein such labels areexpressly not meant to convey quality, or any form of preference orprejudice, but merely to conveniently distinguish among the separatesets. Wherever multiple embodiments serve to illustrate variations inprocess, method, and/or program instruction features, other embodimentsare contemplated that in accordance with a predetermined or adynamically determined criterion perform static and/or dynamic selectionof one of a plurality of modes of operation corresponding respectivelyto a plurality of the multiple embodiments. Numerous specific detailsare set forth in the following description to provide a thoroughunderstanding of the invention. The details are provided for the purposeof example and the invention may be practiced according to the claimswithout some or all of the specific details. For the purpose of clarity,technical material that is known in the technical fields related to theinvention has not been described in detail so that the invention is notunnecessarily obscured.

INTRODUCTION

This introduction is included only to facilitate the more rapidunderstanding of the Detailed Description. The invention is not limitedto the concepts presented in the introduction, as the paragraphs of anyintroduction are necessarily an abridged view of the entire subject andare not meant to be an exhaustive or restrictive description. Forexample, the introduction that follows provides overview informationlimited by space and organization to only certain embodiments. There arein fact many other embodiments, including those to which claims willultimately be drawn, which are discussed throughout the balance of thespecification.

Enhanced mesh network performance is provided by computation of a pathmetric with respect to multi-hop paths between nodes in a mesh networkand determination of a path through the mesh network that is optimalaccording to the path metric. Information, such as in the form of datapackets, is communicated in the mesh network according to the determinedpath. Nodes in the mesh network are enabled to communicate via one ormore wireless links, one or more wired links, or both. Each wirelesslink is tuned to a specific channel (i.e. the channel is assigned to orassociated with the wireless link), and all wireless links use a singlechannel or alternatively various wireless links use a plurality ofchannels, such that communication is enabled to occur in parallel overthe channels. The assignment of channels to wireless links is permanent,in some embodiments, or temporary (varying over time), in otherembodiments.

The path metric optionally includes an effective bandwidth path metrichaving elements (listed from highest to lowest conceptual priority)including an inverse of a sustainable data rate, a number of wirelesslinks, and a number of wireless and wired links. The sustainable datarate is a measure of communication bandwidth that is deliverable by apath for a significant period of time. A higher sustainable data rateindicates a relatively better path. The number of wireless links is ameasure of the amount of wireless communication resources used along thepath. A lower number of wireless links indicates a relatively betterpath. The number of wireless and wired links (or total links) is ameasure of wireless and wired communication resources used along thepath. A lower number of total links indicates a relatively better path.

The path through the mesh network is managed by one or more mesh routingprotocols. The routing protocols optionally stores topologicalinformation about the mesh network according to links, where a linkbetween a pair of nodes in the mesh network indicates the pair of nodesis enabled to communicate with each other. In some usage scenarios, apath between the pair of mesh nodes traverses other mesh nodes and thusincludes one or more links. In other words, a path having a single linkindicates the pair of mesh nodes are enabled to communicate directlywith each other, and a path having two or more links indicatescorresponding intermediary nodes. A routing protocol optionally computesa path between two mesh nodes based on links (and associated linkcharacteristics) the routing protocol is aware of. The path computationoptionally discovers a path having a highest (or relatively higher)throughput (or bandwidth). The path computation optionally finds a pathhaving a lowest (or a relatively lower) traversal latency. The pathcomputation optionally determines a path having a lowest (or relativelylower) packet loss. Various path computations are directed to select apath according to any computation of maximized bandwidth, minimizedlatency, and minimized packet loss, according to various embodiments.The computed path is then optionally used for delivering traffic betweenthe nodes the path is between.

Links in a mesh network are wireless, wired, or both, and each node inthe mesh implements any number and combination of wireless and wiredinterfaces. Transmissions via the wireless interfaces are broadcast innature, so any two wireless interfaces that are tuned to the samechannel and are within transmission range of each other optionally forma wireless link. Similarly, any two wired interfaces that are coupledtogether optionally form a wired link.

Wireless transmissions on the same channel interfere with each otherwhen transmitting nodes are within interference range of each other.However, wireless transmissions on non-overlapping channels do notinterfere with each other. Thus a node having more than one wirelessinterface, each assigned to a unique channel, is enabled tosimultaneously communicate via each of the wireless interfaces. Wiredtransmissions, in contrast, do not interfere with transmissions on anyother wired or wireless links.

Each link has an associated link metric or cost that reflectsdesirability of the link with respect to forwarding traffic, i.e. a linkhaving a lower cost is relatively more attractive for communicatingdata. Some metrics have associated multiple characteristics orsub-metrics that are combinable in various ways to arrive at an overalllink metric. Link sub-metrics include any combination of raw data rate,link utilization, tendency of the link to lose data (referred to aslossy-ness hereinafter), available bandwidth, and other characteristicsof the link.

Various combinations of metrics and other relevant characteristics (suchas current channel assignment) associated with each link are used by amesh routing protocol to compute best or relatively better paths fordelivering traffic between nodes of the mesh network. A path metric orcost is a function of the individual link metrics, costs, andcharacteristics associated with the links of the path. Various pathmetrics are computed for the same path according to differently chosenindividual link metrics, costs, and characteristics, and differingmanners of combining the individual link metrics, costs, andcharacteristics, according to various embodiments.

The path metric computation is performed for a mesh network having aknown set of links, each operating according to a respective channelassignment, and each having respective associated cost metrics. The pathmetric computation provides a set of best paths from each node in themesh network to all other nodes in the mesh network, i.e. the mostefficient communication pathways between the nodes of the mesh network.

FIG. 1 illustrates an embodiment of a mixed wireless and wired meshnetwork having a collection of nodes each including at least onewireless interface (such as Node 100A having wireless interface 121Aoperating on channel 1). Some of the nodes include more than onewireless interface (such as Node 100S having wireless interfaces 121Sand 122S operating on channels 1 and 2, respectively). Some of the nodesinclude a wired interface (such as Nodes 100C and 100S having respectivewired interfaces coupled to wired link 110CS). Communications travelingvia wireless links on the same channel (such as wireless links 111BS and111DS on channel 2) may interfere with each other, but do not interferewith transmissions on other channels. Communications carried via wiredlinks (such as via wired links 110CS and 110BE) do not interfere witheach other or any other wireless link.

In the figure, element identifiers beginning with “100” are associatedwith nodes of the mesh network (such as Nodes 100A and 100B). Elementidentifiers beginning with “12” are representative of wirelessinterfaces, with the third character of the identifier describing achannel associated with the wireless interface, and the last characterof the identifier indicating the node the wireless interface is includedin. An example of a wireless interface identifier is wireless interface125F operating on channel 5 and included in Node 100F. Elementidentifiers starting with “111” represent wireless links formed viawireless interfaces, with the fourth and last characters of theidentifier indicating nodes the wireless link couples. An example of awireless link is wireless link 111EH coupling Nodes 100E and 100H.Element identifiers starting with “110” are used for wired links, withthe fourth and last characters of the identifier indicating nodes thewired link couples. An example of a wired link is wired link 110BEcoupling Nodes 100B and 100E.

Example Embodiments

In concluding the introduction to the detailed description, what followsis a collection of example embodiments, providing additional descriptionof a variety of embodiment types in accordance with the concepts taughtherein; these examples are not meant to be mutually exclusive,exhaustive, or restrictive; and the invention is not limited to theseexample embodiments but rather encompasses all possible modificationsand variations within the scope of the issued claims.

A first illustrative combination of a system comprising means fordetermining an effective wireless bandwidth for a path according to oneof a plurality of techniques, the path having a length of contiguouswireless links; and means for selecting one of the techniques based atleast in part on the length.

The first illustrative combination further comprising means fordetermining a best path through a mesh network that includes thecontiguous wireless links. The foregoing illustrative combinationfurther comprising means for routing traffic according to the best path.The foregoing illustrative combination wherein the mesh network includesa plurality of nodes. The foregoing illustrative combination wherein atleast two of the nodes are enabled to route a portion of the traffic viaa wired link. The foregoing illustrative combination wherein at least apair of the nodes are enabled to route the portion of the traffic via awireless link. The foregoing illustrative combination wherein thewireless link is one of the contiguous wireless links.

The first illustrative combination wherein the means for selectingselects a first one of the techniques if the length is less than athreshold. The foregoing illustrative combination wherein the means forselecting selects a second one of the techniques if the length isgreater than the threshold. The foregoing illustrative combinationwherein the means for selecting selects the second one of the techniquesif the length is equal to the threshold.

The first illustrative combination wherein the means for determiningcomprises means for calculating the effective wireless bandwidth as afunction of a reciprocal of an inverse effective data rate, the inverseeffective data rate being a sum of respective reciprocal bandwidthscorresponding to each of the contiguous wireless links.

The first illustrative combination wherein the means for determiningcomprises means for calculating the effective wireless bandwidth as afunction of a plurality of inverse effective data rates, each of theinverse effective data rates corresponding to a respective set ofcontiguous wireless links, the sets of contiguous wireless linksincluding all sequences of wireless links in the contiguous wirelesslinks having a respective length equal to a threshold. The foregoingillustrative combination wherein the function selects a minimumbandwidth based at least in part on the inverse effective data rates.The foregoing illustrative combination wherein the minimum bandwidthcorresponds to a minimum of reciprocals of the inverse effective datarates.

A second illustrative combination of a system comprising a processor; atleast one interface coupled to the processor; wherein the processor isenabled to execute instructions to determine an effective wirelessbandwidth of a path according to one of a plurality of techniquesselected based at least in part on a length of the path; and wherein thepath is via a plurality of contiguous wireless links equal in number tothe length.

The foregoing illustrative combination wherein the interface is at leastone of a wireless interface and a wired interface. The foregoingillustrative combination wherein the processor is further enabled toexecute further instructions to determine a best path through a meshnetwork that includes the contiguous wireless links. The foregoingillustrative combination wherein the processor is further enabled toexecute additional instructions to route traffic according to the bestpath. The foregoing illustrative combination wherein the processor isincluded in one of a plurality of nodes included in the mesh network.The foregoing illustrative combination wherein the at least oneinterface implements an endpoint of at least one link of the contiguouswireless links.

A third illustrative combination of a method comprising of computing aneffective wireless bandwidth for a path according to one of a pluralityof techniques selected based at least in part on a length of the path;and wherein the path is via a plurality of contiguous wireless linksequal in number to the length.

A fourth illustrative combination of the third illustrative combinationfurther comprising computing a best path through a mesh network thatincludes the contiguous wireless links. A fifth illustrative combinationof the fourth illustrative combination further comprising routingtraffic according to the best path.

A sixth illustrative combination of a computer readable medium having aset of instructions stored therein which when executed by a processingelement causes the processing element to perform operations comprisingcomputing an effective wireless bandwidth for a path according to one ofa plurality of techniques selected based at least in part on a length ofthe path; wherein the path is via a plurality of contiguous wirelesslinks equal in number to the length.

Any of the second, third, and sixth illustrative combinations, wherein afirst one of the techniques is selected if the length is less than athreshold. The foregoing illustrative combination wherein a second oneof the techniques is selected if the length is greater than thethreshold. The foregoing illustrative combination wherein the second oneof the techniques is selected if the length is equal to the threshold.

Any of the second, third, and sixth illustrative combinations, whereinat least one of the techniques includes calculating the effectivewireless bandwidth as a function of a reciprocal of an inverse effectivedata rate, the inverse effective data rate being a sum of respectivereciprocal bandwidths corresponding to each of the contiguous wirelesslinks.

Any of the second, third, and sixth illustrative combinations, whereinat least one of the techniques includes calculating the effectivewireless bandwidth as a function of a plurality of inverse effectivedata rates, each of the inverse effective data rates corresponding to arespective set of contiguous wireless links, the sets of contiguouswireless links including all sequences of wireless links in thecontiguous wireless links having a respective length equal to athreshold. The foregoing illustrative combination wherein the functionselects a minimum bandwidth based at least in part on the inverseeffective data rates. The foregoing illustrative combination wherein theminimum bandwidth corresponds to a minimum of reciprocals of the inverseeffective data rates.

A seventh illustrative combination of the sixth illustrative combinationwherein the operations further comprise computing a best path through amesh network that includes the contiguous wireless links. An eighthillustrative combination of the seventh illustrative combination whereinthe operations further comprise routing traffic according to the bestpath.

Any of the fifth and eighth illustrative combinations, wherein the meshnetwork includes a plurality of nodes. The foregoing illustrativecombination wherein at least two of the nodes are enabled to route aportion of the traffic via a wired link. The foregoing illustrativecombination wherein at least a pair of the nodes are enabled to routethe portion of the traffic via a wireless link. The foregoingillustrative combination wherein the wireless link is one of thecontiguous wireless links.

A ninth illustrative combination of a system comprising means forevaluating a first cost associated with traversing a first path of linksin a mesh network, the first path being associated with a source nodeand a destination node of the mesh network; means for evaluating asecond cost associated with traversing a second path of links in themesh network, the second path being associated with the source and thedestination nodes; wherein the last link of the first path is a wiredlink; and wherein the last link of the second path is a wireless link.

The foregoing illustrative combination wherein the first cost is a firstcurrent cost and the first path is a first current path; and furthercomprising means for replacing a first minimum cost having an associatedfirst best path with the first current cost and replacing the first bestpath with the first current path if the first current cost is less thanthe first minimum cost. The foregoing illustrative combination whereinthe second cost is a second current cost and the second path is a secondcurrent path; and further comprising means for replacing a secondminimum cost having an associated second best path with the secondcurrent cost and replacing the second best path with the second currentpath if the second current cost is less than the second minimum cost.The foregoing illustrative combination further comprising means forselecting a routing path that corresponds to the respective best pathassociated with the minimum of the first and the second minimum costs.The foregoing illustrative combination further comprising means forrouting traffic along the routing path.

The ninth illustrative combination wherein the means for evaluating thefirst cost comprises means for determining an effective bandwidth forany contiguous wireless links along the first path. The ninthillustrative combination wherein the means for evaluating the secondcost comprises means for determining an effective bandwidth for anycontiguous wireless links along the second path.

A tenth illustrative combination of a system comprising a processor; atleast one interface coupled to the processor; wherein the processor isenabled to execute instructions to determine respective first and secondcosts associated with traversing respective first and second paths oflinks in a mesh network; wherein the last link of the first path is awired link; and wherein the last link of the second path is a wirelesslink.

The foregoing illustrative combination wherein the interface is at leastone of a wireless interface and a wired interface. The foregoingillustrative combination wherein each of the paths are associated with asource node and a destination node. The foregoing illustrativecombination wherein the first cost is a first current cost and the firstpath is a first current path; and wherein the processor is furtherenabled to execute further instructions to replace a first minimum costhaving an associated first best path with the first current cost and toreplace the first best path with the first current path if the firstcurrent cost is less than the first minimum cost. The foregoingillustrative combination wherein the second cost is a second currentcost and the second path is a second current path; and wherein theprocessor is enabled to further execute additional instructions toreplace a second minimum cost having an associated second best path withthe second current cost and to replace the second best path with thesecond current path if the second current cost is less than the secondminimum cost. The foregoing illustrative combination wherein theprocessor is further enabled to execute other instructions to select arouting path that corresponds to the respective best path associatedwith the minimum of the first and the second minimum costs.

The tenth illustrative combination wherein the first cost is calculatedbased at least in part on bandwidth reduction due to any contiguouswireless links along the first path. The tenth illustrative combinationwherein the second cost is calculated based at least in part onbandwidth reduction due to any contiguous wireless links along thesecond path.

An eleventh illustrative combination of a method comprising evaluatingrespective first and second costs associated with traversing respectivefirst and second paths of links in a mesh network; wherein the last linkof the first path is a wired link; and wherein the last link of thesecond path is a wireless link.

The foregoing illustrative combination wherein each of the paths areassociated with a source node and a destination node. The foregoingillustrative combination wherein the first cost is a first current costand the first path is a first current path; and further comprising ifthe first current cost is less than a first minimum cost associated witha first best path, then replacing the first minimum cost with the firstcurrent cost and replacing the first best path with the first currentpath. The foregoing illustrative combination wherein the second cost isa second current cost and the second path is a second current path; andfurther comprising if the second current cost is less than a secondminimum cost associated with a second best path, then replacing thesecond minimum cost with the second current cost and replacing thesecond best path with the second current path. The foregoingillustrative combination further comprising selecting a routing paththat corresponds to the respective best path associated with the minimumof the first and the second minimum costs. The foregoing illustrativecombination further comprising routing traffic along the routing path.

The eleventh illustrative combination wherein the evaluating of thefirst cost comprises determining an effective bandwidth for anycontiguous wireless links along the first path. The eleventhillustrative combination wherein the evaluating of the second costcomprises determining an effective bandwidth for any contiguous wirelesslinks along the second path.

A twelfth illustrative combination of a computer readable medium havinga set of instructions stored therein which when executed by a processingelement causes the processing element to perform operations comprisingcomputing respective first and second costs associated with traversingrespective first and second paths of links in a mesh network, each ofthe paths being associated with a source node and a destination node ofthe mesh network; wherein the last link of the first path is a wiredlink; and wherein the last link of the second path is a wireless link.

The foregoing illustrative combination wherein the first cost is a firstcurrent cost and the first path is a first current path; and wherein theoperations further comprise if the first current cost is less than afirst minimum cost associated with a first best path, then replacing thefirst minimum cost with the first current cost and replacing the firstbest path with the first current path. The foregoing illustrativecombination wherein the second cost is a second current cost and thesecond path is a second current path; and wherein the operations furthercomprise if the second current cost is less than a second minimum costassociated with a second best path, then replacing the second minimumcost with the second current cost and replacing the second best pathwith the second current path. The foregoing illustrative combinationwherein the operations further comprise selecting a routing path thatcorresponds to the respective best path associated with the minimum ofthe first and the second minimum costs. The foregoing illustrativecombination wherein the operations further comprise routing trafficalong the routing path.

The twelfth illustrative combination wherein the operations furthercomprise calculating a bandwidth reduction due to any contiguouswireless links along the first path. The foregoing illustrativecombination wherein the first cost is based at least in part on thebandwidth reduction. The twelfth illustrative combination wherein theoperations further comprise calculating a bandwidth reduction due to anycontiguous wireless links along the second path. The foregoingillustrative combination wherein the second cost is based at least inpart on the bandwidth reduction.

A thirteenth illustrative combination of a method comprising determiningan effective wireless bandwidth for a path according to a firsttechnique if a length of the path is less than a threshold; anddetermining the effective wireless bandwidth according to a secondtechnique if the length is not less than the threshold; and wherein thepath is via a plurality of contiguous wireless links equal in number tothe length.

The thirteenth illustrative combination wherein the first techniquecomprises calculating the effective wireless bandwidth as a function ofa reciprocal of an inverse effective data rate, the inverse effectivedata rate being a sum of respective reciprocal bandwidths correspondingto each of the contiguous wireless links.

The thirteenth illustrative combination wherein the second techniquecomprises calculating the effective wireless bandwidth as a function ofa plurality of inverse effective data rates, each of the inverseeffective data rates corresponding to a respective set of contiguouswireless links, the sets of contiguous wireless links including allsequences of wireless links in the contiguous wireless links having arespective length equal to the threshold. The foregoing illustrativecombination wherein the function selects a minimum bandwidth based atleast in part on the inverse effective data rates. The foregoingillustrative combination wherein the minimum bandwidth corresponds to aminimum of reciprocals of the inverse effective data rates.

A fourteenth illustrative combination of a method comprising determininga best path through a mesh network, the best path being via a pluralityof wireless links; routing traffic via the best path; wherein thedetermining comprises computing an effective wireless bandwidth for anumber of contiguous wireless links of the wireless links. The foregoingillustrative combination wherein the best path is further via at leastone wired link.

The fourteenth illustrative combination wherein the computing of theeffective wireless bandwidth comprises if the number of contiguouswireless links is less than a threshold, then determining the effectivewireless bandwidth as a reciprocal of a sum of reciprocal bandwidthscorresponding to each of the contiguous wireless links. The foregoingillustrative combination wherein the computing of the effective wirelessbandwidth further comprises if the number of contiguous wireless linksis not less than the threshold, then determining the effective wirelessbandwidth according to a minimum of a set of sums, each of the setcorresponding to a respective reciprocal of a respective sum of arespective set of reciprocal bandwidths for each possible path having arespective length equal to the threshold and being encompassed by thecontiguous wireless links.

Any of the foregoing illustrative combinations referring to contiguouswireless links wherein the contiguous wireless links operate accordingto a single channel.

Any of the foregoing illustrative combinations referring to a thresholdwherein the threshold is predetermined.

Effective Bandwidth Path Metric

A path metric along a path that includes wireless links is dependent onthe level of wireless interference along the path because interferencereduces throughput and increases packet latency and loss. Interference,in some usage scenarios, depends on the channel assignment of thewireless links and on the order of wireless and wired links along thepath because a wired mesh link may separate the sequence of wirelesslinks before the wired link in the path and the sequence of wirelesslinks after the wired link in the path into non-interfering zones.Therefore, the path metric takes into account not only the individualmetrics of each link along a path, but also the order the links appearalong the path.

A path metric called “effective bandwidth” is defined that takes intoaccount both wireless and wired links, and incorporates the availablebandwidth along each link in the path along with effects of interferenceof consecutive wireless links in the path that are assigned to the samechannel. A path computation technique is then defined that given a setof links, computes the best possible paths from a node to all othernodes reachable through the set of links, according to the effectivebandwidth path metric. The path metric incorporates the effects ofinterference along a multi-hop path that includes wireless and wiredlinks, where each node optionally has more than one wireless and/orwired interface.

The effective bandwidth path metric has three components, inlexicographic (or priority) order: inverse of the sustainable data rate,number of wireless links, and total number of links. The inverse of thesustainable data rate is the most significant component of the pathmetric and is a measure of the inverse of the data rate sustainable onthe path. The metric incorporates the current data rate of each linkalong the path and also depends on the order in which wired and wirelesscommunications links appear in the path, as well as the channel assignedto each wireless link. The lower the inverse of the sustainable datarate (e.g., the higher the sustainable data rate), the better the path.

The number of wireless links along a path is a measure of the amount ofwireless communication resources that are used along the path, andreflects the level of interference generated in the network and possiblyalong the path itself, as well as the probability of packet loss. Thatis, the more wireless links a packet has to traverse, the more likelythe packet will be dropped due to full router queues, or that the packetwill collide with other packets if the link is wireless. The smaller thenumber of wireless links along a path, the more desirable the path.

The total number of links is the least significant part of the pathmetric, and is a measure of the amount of (wired and wireless) networkresources that are used along the path and also reflects the probabilityof packet loss. The lower the total number of links in a path, the moredesirable the path.

Conceptually the way two paths are compared according to thelexicographic ordering of the three components (inverse of thesustainable data rate, number of wireless links, and total number oflinks) is expressed by the following formula, where InvSR stands forinverse sustainable data rate, W stands for the number of wireless linksand N stands for the total number of links along the path. To accountfor the dynamics of the wireless environment, the path computationtechnique optionally uses a threshold parameter Delta (e.g., Delta=0.1,0.2, or some other similar small value) when comparing the reciprocal ofthe sustainable data rate. The path comparison formula for paths 1 and 2having respective inverse sustainable data rates of InvSR1 and InvSR2,having respective numbers of wireless links of W1 and W2, and havingrespective total numbers of wireless links of N1 and N2 is:

(InvSR1,W,N1)<(InvSR2,W2,N2) if

(InvSR1/InvSR2<(1−Delta)) OR

((1−Delta)<=InvSR1/InvSR2<=1) AND (W1<W2) OR

((1−Delta)<=InvSR1/InvSR2<=1) AND (W1==W2) AND (N1<N2)

Inverse Sustainable Data Rate Computation

The most significant component of the effective bandwidth metric, theinverse sustainable data rate, attempts to measure the effectivebandwidth a path is enabled to carry for substantial periods of time.

The inverse sustainable data rate is computed based on the availablebandwidth at each link. The available bandwidth is computed by a routingprotocol or by a link layer based on information collected at the linklayer and also optionally at a network layer. Possible inputs into thecomputation of the available bandwidth metric are raw data rate, linkutilization, link availability, and lossy-ness. Information on themetric associated with a link and its channel assignment is discoveredby the routing protocol along with discovering the link itself.

A path is divided into a set of segments (or sub-paths) such that themetric of each segment is computable independently of the metrics of theother segments, and the metric for the entire path is the minimum of thebandwidths of the segments. In some embodiments, segment boundaries arechosen to coincide with wired links, since in some usage scenarios thewired links separate a path into non-interfering segments.

Consider two nodes u and v coupled by link(u,v). Let B(u,v) denoteavailable bandwidth on link(u,v). Consider a segment P* having n linkssuch that the available bandwidth of the i^(th) link is B(i), where1<=i<=n. The links in the segment P* are divided into (m+1) differentsets, where m is the total number of distinct wireless channels in usein the segment. Set 0 includes all wired links, and Set k includes allwireless links on channel k. For 0<=k<=m, let SR(P*, k) be thesustainable bandwidth across all the links within segment P* in Set k.Note that transmissions on a link in one set do not interfere with, andare independent of the transmissions on a link in any other set. Hence,the sustainable bandwidth across the segment P* is given by the minimumvalue of SR(P*, k), for 0<=k<=m. The minimum value represents thesustainable data rate across segment P* as a scalar value:

SR(P*)=minimum{0<=k<=m}SR(P*,k).

A vector representation of the sustainable data rate is a vector of size(m+1):

vectorSR(P*)=(SR(P*,0),SR(P*,1) . . . SR(P*,m)).

First consider Set 0, i.e. all wired links within the segment P*. Sincetransmissions on wired links do not interfere with each other, thesustainable data rate across wired links in the segment P* is given by:

SR(P*,0)=minimum{1<=i<=n such that link i is a wired link}B(i).

Next consider Set k, i.e. all wireless links within segment P* that areassigned to channel k. Let Assign(i, k) be a Boolean variable that istrue if link i is assigned to channel k. Hence, the time required totransmit a bit across all the hops which are on channel k is given by:

T(P*,k)=sum{1<=i<=n such that Assign(i,k) is True}1/B(i).

In the worst case, all links that are assigned to channel k within thesegment P* are within interference range of each other. Recall that thesustainable data rate across all the wireless links in Set k within thesegment P* is given by SR(P*, k). Therefore, a lower bound on thesustainable data rate SR(P*, k) is given by the inequality SR(P*,k)>=1/T(P*, k). The inequality evolves into a strict equality wheneverall the wireless links within a segment assigned to channel k interferewith one another. Hence:

1/SR(P*,k)<=sum{1<=i<=n such that Assign(i,k) is True}1/B(i)

In some usage scenarios, all the wireless links within a segment thatare assigned to the same channel do not interfere with each other. Thisoccurs, for example, when the links are not within interference range ofone another. In some environments, the interference range is larger thanthe transmission range, and in some situations is twice as large as thetransmission range. Assume that the bandwidth reduction (or degradation)across a sequence of wireless hops ceases (or is ignorable) afterIntfHops hops, where IntfHops is a small integer, such as 4 or 5. Seethe section “Contiguous Wireless Links Sustainable Data Rate”, locatedelsewhere herein, for details of a computation of the sustainable datarate across a contiguous sequence of wireless links on the same channelassuming bandwidth degradation after IntfHops is ignorable.

Returning now to the decomposition of a path P into a series of segmentsP1, P2 . . . Ph, the scalar and vector representations of thesustainable data rate across the entire path P are respectively:

SR(P)=minimum(SR(P1),SR(P2) . . . SR(Ph)), and

vectorSR(P)=vectorMin(SR(P1),SR(P2) . . . SR(Ph));

where for two vectors vectorX=(X0, X1 . . . Xm) and vectorY=(Y0, Y1 . .. Ym) vectorMin=(minimum(X0, Y0), minimum (X1, Y1) . . . minimum (Xm,Ym)).

It is convenient to use the reciprocal of the sustainable data rate,termed the inverse of the sustainable data rate, and denoted InvSR:

InvSR(P*)=maximum{0<=k<=m}InvSR(P*,k), where

InvSR(P*,k)=1/SR(P*,k).

The scalar and vector representations are thus respectively:

InvSR(P)=maximum(InvSR(P1),InvSR(P2) . . . InvSR(Ph)), and

vectorinvSR(P)=vectorMax(InvSR(P1),InvSR(P2) . . . InvSR(Ph));

where for two vectors vectorX=(X0, X1 . . . Xm) and vectorY=(Y0, Y1 . .. Ym) vectorMax=(maximum(X0, Y0), maximum (X1, Y1) . . . maximum (Xm,Ym)).

FIG. 2 illustrates portions of the mesh network of FIG. 1 for an examplecalculation of an effective bandwidth metric. A five hop path isillustrated, from Node 100G to Node 100C, and is analyzed according totwo segments: X (from Node 100G to Node 100B) and Y (from Node 100B toNode 100C). The sustainable data rate along the path is computedaccording to the two segments X and Y.

For segment X (from Node 100G to Node 100B):

InvSR(X,wired)=1/bandwidth(wired link 110BE); // Note that “wired” isalso optionally known as channel 0

InvSR(X,channel 3)=1/bandwidth(wireless link 111DG)+1/bandwidth(wirelesslink 111DE); and

InvSRSegmentX=maximum(InvSR(X,wired),InvSR(X,channel 3)).

For segment Y (from Node 100B to Node 100C):

InvSR(Y,wired)=1/bandwidth(wired link 110CS);

InvSR(Y,channel 2)=1/bandwidth(wireless link 111BS); and

InvSRSegmentY=maximum(InvSR(Y,wired),InvSR(Y,channel 2)).

The (inverse of) the sustainable data rate for the entire path from Node100G to Node 100C is thus the scalar value:

maximum(InvSRSegmentX,InvSRSegmentY).

The vector representation is:

vectorinvSR=(InvSR(wired),null,InvSR(channel2),InvSR(channel 3)),

where the null value corresponds to a lack of channel 1 along the path,and

InvSR(wired)=maximum(InvSR(X,wired),InvSR(Y,wired)).

The effective bandwidth metric calculation then combines the inversesustainable data rate for the path along with the number of wireless andtotal links for the path. According to the path in FIG. 2, the number ofwireless links along the path is three, and the total number of links isfive.

Path Computation

An embodiment of a path computation technique is based on the foregoingeffective bandwidth metric and computes optimal paths from a source nodesrc to all other reachable nodes in a mesh network. The embodiment isdescribed for a special case where each node of the mesh has at most onewireless interface and all of the wireless interfaces are assigned tothe same channel.

The path computation technique maintains, for any node x, selectedvariables associated with up to two paths. For each of the paths, thevariables maintained optionally include respective cost and predecessorinformation. In some embodiments, the variables maintained omit otherinformation about the paths (such as nodes along each path). In thefollowing discussion, a prefix of “0” denotes a wired (or Ethernet)interface while a prefix of “1” denotes a wireless interface. The pathsare:

-   -   Path[0](x): The currently known minimum cost path from node src        to node x such that the last link is an Ethernet link; and    -   Path[1](x): The currently known minimum cost path from node src        to node x such that the last link is a wireless link.

Let Cost[i](x) denote the cost of the path Path[i](x), for i=0, 1.Cost[i](x) is represented by a 3-tuple where the first entry is avector. Thus for i=0, 1:

Cost[i](x)=(vectorInvSR[i](x),num_wireless_links[i](x),num_hops[i](x)).

The cost is alternatively represented by a 3-tuple where the first entryis a scalar value of the inverse of the sustainable data rate:

Cost[i](x)=(InvSR[i](x),num_wireless_links[i](x),num_hops[i](x)).

Let Cost(x) denote the lexicographic-computed minimum of Cost[0](x) andCost[1](x). Hence:

Cost(x)=lexicographic_minimum(Cost[0](x),Cost[1](x)),

where lexicographic_minimum is computed according to the foregoing pathcomparison formula for paths having respective inverse sustainable datarates.

The path computation technique maintains predecessor information forpaths Path[0](x) and Path[1](x). The representation of the predecessorof a node includes an identifier of a parent node and a type of shortestpath from the parent node to the node (i.e. via a wired/Ethernet orwireless interface). Thus for i=0, 1 the predecessor at node x forPath[i](x) is given by:

Pred[i](x)=(parent[i](x),type_from_parent[i](x)).

Similar to Dijkstra's algorithm, the path computation technique proceedsby “marking” nodes one at a time. A set of “unmarked” nodes ismaintained, and during each iteration a one node y among the unmarkednodes having the minimum Cost(y) is “marked”. Then variables Cost[0](x)and Cost[1](x) of all unmarked nodes that are neighbors of the markednode y are updated (or reduced) via a process termed relaxation (see thesection “Path Computation Implementation”, located elsewhere herein, formore information). Appropriate variables are maintained and updated forup to two paths (corresponding to wired and wireless terminating links),thus enabling computation of an effective bandwidth path metriccorresponding to possible optimal paths.

The computation also estimates bandwidth degradation across a contiguoussequence of wireless links by maintaining additional variables for apath ending in a wireless link:

-   -   WirelessHops[1](v)—Number of contiguous wireless links        immediately preceding node v in the best known path to node v        such that the last link is a wireless link; and    -   WirelessTotalInvSR[1](v)—Inverse of the sustainable data rate on        the entire sequence of contiguous wireless links immediately        preceding node v in the best known path to node v such that the        last link is a wireless link.

In some embodiments, the path computation assumes that any two wirelesslinks (of a contiguous sequence of wireless links) that are on the samechannel do interfere with each other. Even though interference within acontiguous sequence of wireless links ceases (or in some circumstancesis ignorable) after links are IntfHops apart, the assumption tends topenalize paths with more wireless links even when the paths have highersustainable data rates than paths with fewer wireless links. Theassumption is in addition to penalizing paths having a similarsustainable data rate but a higher number of wireless links (i.e. thenumber of wireless links is second in the lexicographic orderingassociated with path comparison). Use of more wireless resources createsinterference for nearby links and networks and in some usage scenariosis undesirable. In some embodiments, the path computation assumes apenalty on a path proportional to the number of wireless links in thepath while assuming interference between wireless links is negligibleafter IntfHops. The proportional penalty reduces apparent sustainabledata rate by a fixed value at each wireless link even though therespective wireless link do not, in some usage scenarios, reduce thesustainable data rate when there is no additional interferenceexperienced. See the section “Contiguous Wireless Links Sustainable DataRate”, located elsewhere herein, for further details.

FIG. 3 illustrates portions of the mesh network of FIG. 1 for an examplecalculation of optimal paths. For simplicity, the portion is shown withthree of the nodes having only a single wireless interface and a fourthnode having a pair of wireless interfaces. Three of the wirelessinterfaces operate on a single first channel (channel 2) and theremaining wireless interfaces operate on a non-interfering secondchannel (channel 1). The resulting communication pathways are threewireless links, two that interfere with each other (wireless links111BK, and 111BS) and one that does not interfere with the others(wireless link 111ES). Further the portion is shown with only a singlewired link (wired link 110BE). The optimal paths from a source node(Node 100S) to all other illustrated nodes (Nodes 100B, 100E, and 100K)are to be computed. The respective bandwidths assumed for the links are:

bandwidth(111BS)=40,

bandwidth(111ES)=30,

bandwidth(110BE)=30, and

bandwidth(111BK)=40.

The path computation considers two paths from Node 100S to Node 100B.The paths correspond to the previous link being a wired (Ethernet) linkor the previous link being a wireless link. The variables correspondingto the first (previous link is wired) of the two paths are:

-   -   Path[0](Node 100B): [Node 100S]-[Node 100E]-[Node 100B] is a        minimum cost path from Node 100S to Node 100B such that the        previous link is an Ethernet link;    -   Cost[0](Node 100B)=(maximum(1/bandwidth(link 111ES),        1/bandwidth(link 110BE)), 1, 2); and    -   Pred[0](Node 100B)=(Node 100E, 1 (wireless)).

The variables corresponding to the second (previous link is wireless) ofthe two paths are:

-   -   Path[1](Node 100B): [Node 100S]-[Node 100B] is a minimum cost        path from Node 100S to Node 100B such that the previous link is        a wireless link;    -   Cost[1](Node 100B)=(1/bandwidth(link 111BS), 1, 1); and    -   Pred[1](Node 100B)=(Node 100S, null).

If bandwidth(link 111ES) is 30 and bandwidth(link 111BS) is 40, then interms of the path metric, Path[1](Node 100B) has lower cost thanPath[0](Node 100B) since 1/30 is greater than 1/40. However, because ofinterference between transmissions on two wireless links operating onthe same channel (links 111BS and 111BK), the relative cost is reversedat Node 100K.

The path computation further considers two paths (with the previous linkbeing respectively wired and wireless) from Node 100S to Node 100K. Thevariables corresponding to the first of the two paths (i.e. where thelink preceding Node 100K is a wired link) are:

Path[0](Node 100K): No path exists; and

Cost(Node 100K)=(vectorInfinity, Infinity, Infinity).

The variables corresponding to the second of the two paths (i.e. wherethe link preceding Node 100K is a wireless link) are selected from theminimum of two candidate paths:

-   -   Candidate1:    -   Path[1](Node 100K): [Node 100S]-[Node 100B]-[Node 100K], i.e.        Path[1](Node 100B) concatenated with link 111BK; and    -   Cost[1](Node 100K)=(1/bandwidth(link 111BS)+1/bandwidth(111BK),        2, 2), since transmissions on the two wireless links 111BS and        111BK do interfere with each other.    -   Candidate2:    -   Path[1](Node 100K): [Node 100S]-[Node 100E]-[Node 100B]-[Node        100K], i.e. Path[0](Node 100B) concatenated with link 111BK; and    -   Cost[1](Node 100K)=(maximum(1/bandwidth(link 111ES),        1/bandwidth(link 110BE), 1/bandwidth(link 111BK)), 2, 3).        If bandwidth(link 111BK) is 40, then the first candidate        Cost(Node 100K) is ( 1/40+ 1/40, 2, 2) or ( 1/20, 2, 2). If        bandwidth(link 110BE) is 30, then the second candidate Cost(Node        100K) is (maximum( 1/30, 1/30, 1/40), 2, 3) or ( 1/30, 2, 3).        The minimum of the two candidates is selected as ( 1/30, 2, 3).

Path Computation Implementation

FIGS. 4A-D illustrate various aspects of an embodiment of the pathcomputation technique. In the following description of FIGS. 4A-D andassociated pseudo-code, it is useful to understand the followingnotational conventions and context:

-   -   G=(V, E): A directed weighted graph, with a vertex set V        (corresponding to nodes of the mesh network) and an edge set E        (corresponding to wired and wireless links of the mesh network;    -   src: The source node for which all shortest paths are being        computed;    -   S: The set of nodes for which all shortest (best) paths have        been determined;    -   Q: A queue containing all nodes from V not already in S (i.e.        all nodes not having final best paths computed with respect to        src);    -   Adj[v]: The neighbors of node v (i.e. those nodes reachable from        v in one wired or wireless hop); and    -   b(u, v): The available link bandwidth on link(u, v).

The path metric corresponding to a path is a 3-tuple:

(vectorinvSR, num_wireless_links, num_hops)

where:

-   -   vectorinvSR is a vector representation of the inverse of the        sustainable data rate along the path—in a single wireless        interface scenario, the vector is size 2 (i.e. m+1 where m is        one) where member 0 of the vector denotes Ethernet (wired) and        member 1 denotes wireless;    -   num_wireless_links is the number of wireless links along the        path; and    -   num_hops is the total number of hops (or links), wired and        wireless, along the path.

Let Cost[0](v) be the (current minimum) cost metric of the best knownpath to node v such that the last link is an Ethernet (or wired) link.Also:

Pred[0](v)=(parent[0](v),type_from_parent[0](v))

is the predecessor of node v for Path[0](v), where parent[0](v) is theidentifier of the parent node, and type_from_parent[0](v) indicates thetype of path (i.e, Ethernet or wireless) to be taken from the parent.

Similarly, let Cost[1](v) be the (current minimum) cost metric of thebest known path to node v such that the last link is a wireless link.Also:

Pred[1](v)=(parent[1](v),type_from_parent[1](v))

is the predecessor of node v for Path[1](v). For a path ending in awireless link, two additional variables are maintained:

-   -   WirelessHops[1](v) is the number of contiguous wireless links        immediately preceding node v in the best known path to node v        such that the last link is a wireless link; and    -   WirelessTotalInvSR[1](v) is the inverse of the sustainable data        rate on the entire sequence of contiguous wireless links        immediately preceding node v in the best known path to node v        such that the last link is a wireless link.

Let Cost(v) denote the minimum of Cost[0](v) and Cost[1](v). Thus:

Cost(v)=minimum(Cost[0](v),Cost[1](v))

using the foregoing lexicographic-computed comparison for 3-tuples.

FIG. 4A illustrates a top-level flow diagram of an embodiment of thepath computation. Flow begins (“Start” 401) and continues to set variousvariables relating to the computation to starting values (“Initialize”402). It is then determined if there are any remaining nodes to process(“More Nodes?” 403). If not (“No” 403N), then processing is complete(“End” 499). If so (“Yes”, 403Y), then processing continues to selectanother node to process (“Next Node” 404). Best path information for allnodes adjacent to the selected node (i.e. one link away according to thetopology of the mesh network) is then updated (“Process Node Neighbors”405). Processing then flows back to determine if there are additionalnodes to process (“More Nodes” 403).

Processing relating to “Initialize” 402 is described by the followingpseudo-code:

For each node v in V { vectorInvSR[0](v) = vectorInfinity;num_wireless_links[0](v) = Infinity; num_hops[0](v) = Infinity;vectorInvSR[1](v) = vectorInfinity; num_wireless_links[1](v) = Infinity;num_hops[1](v) = Infinity; parent[0](v) = null; type_from_parent[0](v) =NA; parent[1](v) = null; type_from_parent[1](v) = NA; //vectorInvSR[0](src) = 0; num_wireless_links[0](src) = 0;num_hops[0](src) = 0; vectorInvSR[1](src) = 0;num_wireless_links[1](src) = 0; num_hops[1](src) = 0;WirelessHops[1](src) = 0; WirelessTotalInvSR[1](src) = 0; } S = nil; Q =V;where vectorinvSR is of size two and all elements therein are set toeither zero or infinity as appropriate.

Processing relating to “More Nodes?” 403 is described by the followingpseudo-code:

While(Q!=null)

Processing relating to “Next Node” 404 is described by the followingpseudo-code:

S = AddNode(S, u); Q = DeleteNode(Q, u);where u is a node (or vertex in a directed graph context) such that:

Cost(u)=minimum(Cost(v)) over all vertices v in Q.

In other words, u denotes the recently marked vertex.

FIG. 4B illustrates an embodiment of processing associated with “ProcessNode Neighbors” 405 of FIG. 4A. Processing begins (“Start” 405A) andcontinues to check if all neighbor nodes have been completed (“AllProcessed?” 405B). If so (“Yes” 405BY), then processing is complete(“End” 405Z). If not (“No” 405BN), then processing proceeds to select aremaining node (“Next Neighbor Node” 405C). Flow then continues todetermine whether the link type associated with the selected node iswired (i.e. Ethernet) or wireless (“Link Type?” 405D). If the link iswired (“Wired” 405D0), then flow proceeds to determine if the linkenables a better path than previously known (“Evaluate Wired Link”405E). If the link is wireless (“Wireless 405D1), then flow continues todetermine if the link enables a better path than what has beendiscovered before (“Evaluate Wireless Link” 405F). Processing toevaluate a wireless link is slightly different than processing a wiredlink, as described with respect to the FIG. 4C. After completingevaluation of the link (via either of “Evaluate Wired Link” 405E or“Evaluate Wireless Link” 405F) flow proceeds back to determine if moreremain to be processed (“All Processed?” 405B).

Processing associated with “All Processed?” 405B is described by thefollowing pseudo-code:

For each node v in Adj[u]

where processing associated with “Next Neighbor Node” 405C skips node vif v is already present in S.

Processing associated with “Link Type?” 405D is described by thefollowing pseudo-code:

If (type of link(u, v) == Ethernet) {process according to 405E}; If(type of link(u, v) == wireless) {process according to 405F};

FIG. 4C illustrates an embodiment of processing associated with eitherof “Evaluate Wired Link” 405E and “Evaluate Wireless Link” 405F of FIG.4B. Processing begins (“Start” 405EF.1) and proceeds to determine if anew best path is available based on a link currently being evaluated.The currently evaluated link is processed twice, according to twocontexts, a first context where the last link in the path thus far is awired link, and a second context where the last link in the path thusfar is a wireless link. The first context (“Evaluate Wired Last LinkPath” 405EF.2) and the second context (“Evaluate Wireless Last LinkPath” 405EF.3) are evaluated independently and in any order (such as inparallel as illustrated), in some embodiments. After the evaluations,the minimum of the two is chosen (“Select Minimum” 405EF.4). Processingthen continues to determine if a new best path has been discovered(“Better?” 405EF.5). If not (“No” 405EF.5N), then processing is complete(“End” 405EF.99). If so (“Yes” 405EF.5Y), then flow continues to savenew information based on the new path (“Update Parent, Cost, Type”405EF.6). Processing is then complete (“End” 405EF.99).

While the illustrated flow is representative of processing for either ofa wired (or Ethernet) link and a wireless link, the wireless linkprocessing is modified from and is described herein after the wired linkprocessing. Processing associated with “Start” 405EF.1 during evaluationof a wired link is described by the following pseudo-code:

current_metric=Cost[0](v);

Processing associated with “Evaluate Wired Last Link Path” 405EF.2further during evaluation of a wired link is described by the followingpseudo-code:

candidate_metric0 = Cost[0](u); candidate_metric0.vectorInvSR[0 :=Ethernet] = maximum(1/b(u,v), candidate_metric0.vectorInvSR[0 :=Ethernet]); candidate _metric0.num_hops += 1;

Processing associated with “Evaluate Wireless Last Link Path” 405EF.3 isdescribed by the following pseudo-code:

candidate_metric1 = Cost[1](u); candidate_metric1.vectorInvSR[0 :=Ethernet] = maximum(1/b(u,v), candidate_metric1.vectorInvSR[0 :=Ethernet]); candidate_metric1.num_hops += 1;

Processing associated with “Select Minimum” 405EF.4 is described by thefollowing pseudo-code:

min_metric=minimum(candidate_metric°,candidate_metric1);

Processing associated with “Better?” 405EF.5 is described by thefollowing pseudo-code:

If(min_metric<current_metric)

Processing associated with “Update Parent,Cost,Type” 405EF.6 isdescribed by the following pseudo-code:

parent[0](v) = u; If(candidate_metric0 == min_metric) Cost[0](v) =candidate_metric0; type_from_parent[0](v) = 0 // Ethernet (wired) linkIf(candidate_metric1 == min_metric) Cost[0](v) = candidate_metric1;type_from_parent[0](v) = 1 // Wireless linkThe foregoing completes the processing during evaluation of a wiredlink.

Processing associated with a wireless link is a variation compared tothe processing associated with a wireless link, as the followingpseudo-code illustrates. Processing associated with “Start” 405EF.1during evaluation of a wireless link is described by the followingpseudo-code:

current_metric=Cost[1](v);

Processing associated with “Evaluate Wired Last Link Path” 405EF.2further during evaluation of a wireless link is described by thefollowing pseudo-code:

candidate_metric0 = Cost[0](u); candidate_metric0.vectorInvSR[1 :=Wireless] = maximum(1/b(u,v), candidate_metric0.vectorInvSR[1 :=Wireless]); candidate_metric0.num_wireless_links += 1;candidate_metric0.num_hops += 1;

Processing associated with “Evaluate Wireless Last Link Path” 405EF.3 isdescribed by the following pseudo-code:

candidate_metric1 = Cost[1](u); InvB1 = candidate_metric1.vectorInvSR[1:= Wireless]; InvB2 = Wireless _TotalInvSR[1](u) + 1/b(u,v);candidate_metric1.vectorInvSR[1 := Wireless] = maximum(InvB1, InvB2);candidate_metric1.num_wireless_links += 1; candidate_metric1.num_hops +=1;

Processing associated with “Select Minimum” 405EF.4 is described by thefollowing pseudo-code:

min_metric=minimum(candidate_metric°,candidate_metric1);

Processing associated with “Better?” 405EF.5 is described by thefollowing pseudo-code:

If[min_metric<current_metric)

Processing associated with “Update Parent,Cost,Type” 405EF.6 isdescribed by the following pseudo-code:

parent[1](v) = u; If(candidate_metric0 == min_metric) Cost[1](v) =candidate_metric0; type_from_parent[1](v) = 0 // Ethernet (wired) linkWirelessHops[1](v) = 1; WirelessTotalInvSR[1](v) = 1/b(u,v)If(candidate_metric1 == min_metric) Cost[1](v) = candidate_metric1;type_from_parent[1](v) = 1 // Wireless link; WirelessHops[1](v) = 1 +WirelessHops[1](u); WirelessTotalInvSR[1](v) =WirelessTotalInvSR[1](u) + 1/b(u,v)The foregoing completes the processing during evaluation of a wirelesslink.

Contiguous Wireless Links Sustainable Data Rate

Evaluating bandwidth of a set of contiguous wireless links includescomputing an effective bandwidth metric by assuming a wireless linkinterferes only with other wireless links that are on the same channeland within IntfHops wireless links away. In some embodiments, results ofthe computation is used in evaluating paths (such as computationsperformed with respect to one or more elements of FIG. 4B and FIG. 4C).In some embodiments, the results is used by a routing protocol thatcompares paths to each other and computes the effective bandwidth metricfor respective paths.

FIG. 4D illustrates an embodiment of processing associated withdetermining an effective sustainable data rate along a contiguoussequence of wireless links. Processing begins (“Start” 410) and proceedsto determine if the number of contiguous links equals or surpasses athreshold (“>=IntfHops Links?” 411). If not (“no” 411N), then addingreciprocal bandwidths over the path being processed is sufficient (“SumInverse Rates” 412) to determine an effective (inverse) data rate andprocessing is then complete (“End” 498).

If the threshold is met or exceeded (“Yes” 411Y), then an effective(inverse) bandwidth is computed for every contiguous sequence ofwireless links within the path having a length equal to the threshold,and the minimum chosen as the effective (inverse) data rate. Processingfor the sequences begins by determining if more sequences remain to beprocessed in the path (“Another Sequence?” 421). If not (“No” 421), thenthe smallest data rate of all of the sequences is chosen (“SelectMinimum” 422). Processing is then complete (“End” 498). If moresequences remain to be processed (“Yes” 421Y), then flow continues todetermine another sequence to process (“Next Sequence” 423). Theeffective (inverse) data rate for the next sequence is then computed(“Determine Inverse Rate” 424) and then processing flows back todetermine if further sequences remain (“Another Sequence?” 421).

Pseudo-code implementing operations according to FIG. 4D corresponds tothe function Wireless_invSR_Function that receives two arguments:

-   -   vectorinvSR is a vector denoting the reciprocal of available        bandwidth along each link of a contiguous sequence of wireless        links of length p=|vectorInvSR|, where the entry of the vector        is denoted InvSR(i), for i=1, 2 . . . p; and    -   b(l) is available bandwidth of the wireless link appended at the        end of the path.        The pseudo-code also refers to:    -   IntfHops is an (assumed or estimated) number of hops beyond        which there is no additional bandwidth degradation due to        interference between contiguous wireless links operating on the        same channel, and in some scenarios is a small integer such as 4        or 5.

Processing associated with “>=IntfHops Links?” 411 is described by thefollowing pseudo-code:

If(p<IntfHops)

or alternatively as:

If(p>=IntfHops)

Processing associated with “Sum Inverse Rates” 412 is described by thefollowing pseudo-code:

FinalInvSR = 1/b(l) + sum{i=1 to p} InvSR(i) return FinalInvSR

Processing associated with “Another Sequence?” 421, “Select Minimum”422, “Next Sequence” 423, and “Determine Inverse Rate” 424 incombination is described by the following pseudo-code:

InvSR(p+1) = 1/b(l); // Append entry 1/b(l) at the end of the InvSRvector, resulting in a vector size of p+1 FinalInvSR = sum{i=1 toIntfHops} InvSR(i) For(j = 1; j <= p+1 − IntfHops; ++j) { CandidateInvSR= 0; For (i =1; i <= IntfHops; ++i) CandidateInvSR += InvSR(j+i)If(CandiadateInvSR > FinalInvSR) FinalInvSR = CandiadteInvSR } returnFinalInvSR

Node Hardware and Software

FIG. 5 illustrates selected details of hardware aspects of an embodimentof a node. The illustrated node includes Processor 510 coupled tovarious types of storage, including volatile read/write memory (MemoryBanks 501A and 501) via Dynamic Randomly Accessible read/write Memory(DRAM) Memory Interface 502, and non-volatile read/write memory (FLASH503 and Electrically Erasable Programmable Read Only Memory (EEPROM)504). The processor is further coupled to Ethernet Interface 521providing a plurality of Ethernet Ports 522 for establishing wiredlinks, and via PCI Interface 505 to Wireless Interfaces 525A and 525Bfor providing radio communication of packets for establishing wirelesslinks. In some embodiments, one or more of the wireless interfaces arecompatible with an IEEE 802.11 wireless communication standard (such asany of 802.11a, 802.11b, and 802.11g). In some embodiments, one or moreof the wireless interfaces operate (in conjunction with any combinationof other hardware and software elements) to collect statistics withrespect to neighboring nodes of a mesh. The statistics include anycombination of signal strength and link quality, in various embodiments.In some embodiments, one or more of the wireless interfaces areconfigurable to drop all packets below a settable Received SignalStrength Indicator (RSSI) threshold. In some embodiments, one or more ofthe wired interfaces are 10 Mb, 100 Mb, 1 Ggb or 10 Gb compatible. Nodeimplementations include any combination of wireless and wiredinterfaces, such as only a single wireless (or wired) interface, or oneof each type, or two of each type. Other equivalent embodiments of anode are contemplated, as the illustrated partitioning is only oneexample.

The illustrated node optionally functions as any one of the mesh nodesillustrated in FIG. 1 (such as any of Node A 100A, Node S 100S, and soforth). The illustrated wireless interfaces of FIG. 5 enablecommunication between nodes and provide low-level transport for packetsmoving between elements of the mesh, such as by implementing wirelessinterfaces 121S and 122S associated with Node S 1005 of FIG. 1. TheEthernet ports of FIG. 5 provide for wired communication between nodes,such as for implementing wired link 110CS associated with Node C 100Cand Node S 1005 of FIG. 1.

In operation the processor fetches instructions from any combination ofthe storage elements (DRAM, FLASH, and EEPROM) and executes theinstructions. Some of the instructions correspond to execution ofsoftware associated with operations relating to processing for effectivebandwidth path metric computation and path computation using the metric.

FIG. 6 illustrates selected details of software aspects of an embodimentof a node. The illustrated software includes Network Management System(NMS) Manager 650 interfacing to Network Interface Manager 640 andFault, Configuration, Accounting, Performance, and Security (FCAPS)Manager 630. In some embodiments, the NMS interfaces between managementsoftware operating external to the node and software operating internalto the node (such as various applications and FCAPS). The NetworkInterface Manager manages physical network interfaces (such as theEthernet and Wireless Interfaces). The Network Interface Manager assiststhe NMS in passing dynamic configuration changes (as requested by auser) through the management software to FCAPS. In some embodiments,FCAPS includes functions to store and retrieve configurationinformation, and FCAPS functions serve all applications requiringpersistent configuration information. FCAPS, in some embodiments,assists in collecting fault information and statistics and performancedata from various operating modules of the node. FCAPS optionally passesany portion of the collected information, statistics, and data to theNMS.

Kernel Interface 601 interfaces the Managers to Routing and TransportProtocols layer 610 and Flash File System module 602. The RoutingProtocols include all or portions of processing relating to effectivebandwidth path metric computation and path computations using themetric, as well as general processing relating to operation as a node ofthe mesh and forwarding packets. The Transport Protocols include TCP andUDP. The Flash File System module interfaces to Flash Driver 603 that isillustrated conceptually coupled to FLASH file hardware element 503Athat is representative of a flash file system stored in any combinationof FLASH 503 and EEPROM 504 of FIG. 5. Layer-2 Abstraction Layer 611interfaces the Routing and Transport Protocols to Ethernet Driver 621and Radio Driver 625. The Ethernet Driver is illustrated conceptuallycoupled to Ethernet Interface 521 of FIG. 5. The Radio Driver isillustrated conceptually coupled to Wireless Interfaces 525,representative of Wireless Interfaces 525A and 525B of FIG. 5. In someembodiments, the software also includes a serial driver. The software isstored on a computer readable medium (such as any combination of theDRAM, FLASH, and EEPROM elements of FIG. 5), and is executed by theprocessor of FIG. 5. The partitioning illustrated in FIG. 6 is anexample only, and many other equivalent arrangements of layers andmodules are contemplated.

CONCLUSION

Certain choices have been made in the presentation of this disclosuremerely for reasons of convenience in preparing the text and drawings andunless there is an indication to the contrary these choices ofconvenience should not be construed per se as conveying additionalinformation regarding the structure of the embodiments illustrated.Illustrative examples of such choices of convenience include: theparticular organization or assignment of the designations used for thefigure numbering and the particular organization or assignment of theelement identifiers (i.e., the callouts or numerical designators) usedto identify and reference the features and elements of the embodiments.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, the invention is not limitedto the details provided. There are many ways of implementing theinvention. The disclosed embodiments are illustrative and notrestrictive.

It will be understood that many variations in construction, arrangementand use are possible consistent with the teachings and within the scopeof the claims appended to the issued patent. For example, interconnectand function-unit bit-widths, clock speeds, and the type of technologyused may generally be varied in each component block. The names given tointerconnect and logic are merely illustrative, and should not beconstrued as limiting the concepts taught. The order and arrangement offlowchart and flow diagram process, action, and function elements maygenerally be varied. Also, unless specifically stated to the contrary,the value ranges specified, the maximum and minimum values used, orother particular specifications (such as number and type of wired andwireless interfaces; and the number of entries or stages in registersand buffers), are merely those of the illustrative embodiments, may beexpected to track improvements and changes in implementation technology,and should not be construed as limitations.

Functionally equivalent techniques known to those of ordinary skill inthe art may be employed instead of those illustrated to implementvarious components, sub-systems, functions, operations, routines, andsub-routines. It is also understood that many design functional aspectsmay be carried out in either hardware (i.e., generally dedicatedcircuitry) or software (i.e., via some manner of programmed controlleror processor), as a function of implementation dependent designconstraints and the technology trends of faster processing (whichfacilitates migration of functions previously in hardware into software)and higher integration density (which facilitates migration of functionspreviously in software into hardware). Specific variations may include,but are not limited to: differences in partitioning; different formfactors and configurations; use of different operating systems and othersystem software; use of different interface standards, networkprotocols, or communication links; and other variations to be expectedwhen implementing the concepts taught herein in accordance with theunique engineering and business constraints of a particular application.

The embodiments have been illustrated with detail and environmentalcontext well beyond that required for a minimal implementation of manyof aspects of the concepts taught. Those of ordinary skill in the artwill recognize that variations may omit disclosed components or featureswithout altering the basic cooperation among the remaining elements. Itis thus understood that much of the details disclosed are not requiredto implement various aspects of the concepts taught. To the extent thatthe remaining elements are distinguishable from the prior art,components and features that may be so omitted are not limiting on theconcepts taught herein.

All such variations in design comprise insubstantial changes over theteachings conveyed by the illustrative embodiments. It is alsounderstood that the concepts taught herein have broad applicability toother computing and networking applications, and are not limited to theparticular application or industry of the illustrated embodiments. Theinvention is thus to be construed as including all possiblemodifications and variations encompassed within the scope of the claimsappended to the issued patent.

1-29. (canceled)
 30. A method, comprising: computing, at least in partvia a processor, an effective wireless bandwidth for a path according toa first technique when a number of contiguous wireless links along thepath is less than a threshold; computing, at least in part via theprocessor, the effective wireless bandwidth according to a secondtechnique when the number is greater than the threshold; wherein thefirst technique comprises calculating a first effective wirelessbandwidth as a first function of a reciprocal of an inverse resultantdata rate, the inverse resultant data rate being a sum of respectivereciprocal bandwidths corresponding to each of the contiguous wirelesslinks; and wherein the second technique comprises calculating a secondeffective wireless bandwidth as a second function of a plurality ofinverse effective data rates, each of the inverse effective data ratescorresponding to a respective set of contiguous wireless links, each ofthe sets having a respective length equal to the threshold.
 31. Themethod of claim 30, wherein the sets include all sequences of wirelesslinks in the contiguous wireless links having a respective length equalto the threshold.
 32. The method of claim 31, wherein the first functionis a reciprocal function.
 33. The method of claim 31, wherein the secondfunction is a minima function.
 34. The method of claim 31, furthercomprising computing the effective wireless bandwidth according to thesecond technique when the number is equal to the threshold.
 35. Themethod of claim 31, further comprising computing a best path through amesh network that includes the contiguous wireless links.
 36. The methodof claim 35, further comprising determining the best path at least inpart according to the effective wireless bandwidth.
 37. The method ofclaim 36, routing traffic according to the best path.
 38. The method ofclaim 35, wherein the processor is included in a node that is part ofthe mesh network.
 39. The method of claim 38, wherein a wirelessinterface is included in the node.
 40. The method of claim 38, wherein awired interface is included in the node.
 41. A system, comprising: meansfor computing an effective wireless bandwidth for a path according to afirst technique when a number of contiguous wireless links along thepath is less than a threshold; means for computing the effectivewireless bandwidth according to a second technique when the number isgreater than the threshold; wherein the first technique comprisescalculating a first effective wireless bandwidth as a first function ofa reciprocal of an inverse resultant data rate, the inverse resultantdata rate being a sum of respective reciprocal bandwidths correspondingto each of the contiguous wireless links; and wherein the secondtechnique comprises calculating a second effective wireless bandwidth asa second function of a plurality of inverse effective data rates, eachof the inverse effective data rates corresponding to a respective set ofcontiguous wireless links, each of the sets having a respective lengthequal to the threshold.
 42. The system of claim 41, wherein the setsinclude all sequences of wireless links in the contiguous wireless linkshaving a respective length equal to the threshold.
 43. The system ofclaim 42, wherein the first function is a reciprocal function.
 44. Thesystem of claim 42, wherein the second function is a minima function.45. The system of claim 42, further comprising means for computing theeffective wireless bandwidth according to the second technique when thenumber is equal to the threshold.
 46. The system of claim 42, furthercomprising means for computing a best path through a mesh network thatincludes the contiguous wireless links.
 47. The system of claim 46,further comprising means for determining the best path at least in partaccording to the effective wireless bandwidth.
 48. The system of claim47, routing traffic according to the best path.
 49. The system of claim46, wherein the means are included in a node that is part of the meshnetwork.